New edge-directed interpolation

This paper proposes an edge-directed interpolation algorithm for natural im ages. The basic idea is to first estimate local covariance coefficients fro m a low-resolution image and then use these covariance estimates to adapt t he interpolation at a higher resolution based on the geometric duality betw een the low-resolution covariance and the high-resolution covariance. The e dge-directed property of covariance-based adaptation attributes to its capa bility of tuning the interpolation coefficients to match an arbitrarily ori ented step edge. A hybrid approach of switching between bilinear interpolat ion and covariance-based adaptive interpolation is proposed to reduce the o verall computational complexity. Two important applications of the new inte rpolation algorithm are studied: resolution enhancement of grayscale images and reconstruction of color images from CCD samples. Simulation results de monstrate that our new interpolation algorithm substantially improves the s ubjective quality of the interpolated images over conventional linear inter polation.